1. Field of the Invention
The present invention relates in general to an engine, and in particular to a fuel system and arrangement for a marine engine.
2. Description of Related Art
Personal watercraft have become popular in recent years. This type of watercraft is sporty in nature; it turns swiftly, is easily maneuverable, and accelerates quickly. Personal watercraft today commonly carry one rider and one or two passengers.
A relatively small hull of the personal watercraft commonly defines a rider's area above an engine compartment. An internal combustion engine frequently powers a jet propulsion unit which propels the watercraft. A plurality of engine mounts support the engine within the engine compartment in front of a tunnel formed on the underside of the watercraft. The jet propulsion unit is located within the tunnel and is driven by a drive shaft connected to the engine.
Personal watercraft often employ an inline, multi-cylinder, crankcase compression, two-cycle engine. The engine conventionally lies within the engine compartment with the in-line cylinders aligned along a longitudinal axis of the watercraft hull. An exhaust system communicates with the cylinders of the engine and extends to a discharge that is located near the stem of the watercraft. In this manner, exhaust gases are expelled from the watercraft's and the engine compartment.
Air must be supplied to the engine from outside the hull for use in the combustion process. Typically, air flows through one or more ducts in the hull into the engine compartment, and then through an intake system of the engine to combustion chambers of the engine.
Fuel is also supplied to the engine for use in the combustion process. In order to accurately meter the fuel and improve engine operating efficiency and performance, fuel injectors can be used to inject fuel into the combustion chambers or to form a fuel/air charge before such charge enters the combustion chambers. Each injector has an electrically-operated valve which selectively opens and closes, controlling the flow of fuel through the injectors to the engine. Typically, a high pressure fuel pump is used to supply pressurized fuel to each fuel injector via a fuel rail. The fuel system continuously supplies fuel from a fuel tank to the fuel injectors while returning excess fuel to the fuel tank through a return line.
In order to keep the size of the watercraft small and center of gravity low, the engine compartment is made very small, thus necessitating that the engine be compact. One problem with this arrangement is that hot exhaust gases flowing through the exhaust system may be routed very close to other components of the engine, damaging them or resulting in their poor performance. This is true for the fuel pump where the heat from the exhaust system may damage the fuel pump or shorten its useful life. Elevation of the fuel temperate within the delivery and return lines, as well as within the fuel pump, can also affect the fuel air ratio of the charge formed by the fuel injectors.
Some prior watercraft have increased the width of the watercraft in order to separate the fuel supply system from the exhaust system. Such watercraft, however, sacrifice the handling performance of the watercraft due to the resulting wider hull; the wider hull can not turn as sharp.
Moreover, the associated engines have also employed a wider width in order to provide a component arrangement wherein the position of the fuel rail is positioned on one side of the engine, away from the exhaust system, in a suspended position. However, due to the sporty nature of the watercraft, the fuel supply pipe experiences vigorous impact as the watercraft jumps and lands when speeding across the body of water in which it is operated. The high pressure fuel supply pipe thus can be damaged when supported in this position and directly mounted to the hull.